Anything that works on the Sprint/Verizon Touch Pro's that isn't network specific (Sprint TV, VZ Navigator, etc) will work on the Alltel Touch Pro. Some tweaks may need some modification due to carrier verbiage being different in the registry (Alltel may not call PAM "Phone As Modem" as an example), but overall there should be little difference.
As for ROM's, they must be cooked for specific carrier usage in most cases unless they build it as an open device and then you'd have to follow instructions to assign it to the network of your choice, like those found here:
http://forum.ppcgeeks.com/showpost.p...85&postcount=1
Enjoy your new Touch Pro.